Chamber size??

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Sublime69

Sublime69

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Does anyone know what size chambers are on a 74 318??

Also if anyone knows the size chambers on the newer magnum heads(like from a 99 dakota or something)?

Thanks
 
Sorry Sublime69 I don't know what the CC's of the heads are, but is that your Dart for Real? That thing is awsome!!! :thumrigh: What size rims and tires are those? That picture really inspires me to finish my 69 GT. How about some more pics and info on what's been done to the car.

Thanks
-Nick :thumleft:
 
Don't know on the 318 heads but the new magnum heads have a chamber size of approx 60 cc's. BTW, both the 5.2 and 5.9 magnums use the same head.
 
68- 74 318 heads, casting # 2843675 is 60cc, according to the "How To Rebuild Small Block Mopar Engines" book by Taylor/Hofer.
 
purplebeast wrote:
68- 74 318 heads, casting # 2843675 is 60cc
Click to expand...

That matches the casting number that the Mopar Engine book lists, but it does not specify the chamber volume. But the 60cc does match several online references. You should verify that that is the head you have though.

http://www.mopar1.us/Aengine.html
 
Ad a few CCs to any published numbers you read. Most Magnum heads are 62cc
 
Well how come the comp. ratio is so low in 74(8.6) compared to earlyer 68 318 (9.2)? Isint just because of the chamber size difference?

check out this article http://www.carcraft.com/howto/116_0401_318/index.html

In here used stock magnum heads from MP, and it says that they are 59cc chambers. And they decked the block and it gave them 10:1.

So im just trying to figure out what my compression would be if i put these heads on my motor but dont mill the heads or block.

BTW: i am not using Mopar Performance heads, i am using a set from the junk yard. Thats why i dont know if the chambers are different.
 
after 71 they dropped compression by moving the piston pin up. this dropped the piston way down in the bore about .100"

The earlier 318s that are rated in the 9:1 are are lower then that. probably in the *.5-8.8:1 range.

The real bad news is your 318 is likely in the 7.8:1 range.

The only way to know for sure what your compression is ,is to measure everything. Head CC's, Deck hieght and gasket thickness.
 
AdamR said:
after 71 they dropped compression by moving the piston pin up. this dropped the piston way down in the bore about .100"

The earlier 318s that are rated in the 9:1 are are lower then that. probably in the *.5-8.8:1 range.

The real bad news is your 318 is likely in the 7.8:1 range.

The only way to know for sure what your compression is ,is to measure everything. Head CC's, Deck hieght and gasket thickness.
Click to expand...

So the heads are the same from a 68 to a 74?
 
they will have a few differances but for the most part they are the same.

I would have a set of heads milled about .050" and run a thin .028" gasket.

Nice Dart by the way.
 
AdamR said:
they will have a few differances but for the most part they are the same.

I would have a set of heads milled about .050" and run a thin .028" gasket.

Nice Dart by the way.
Click to expand...

Thanks, but if i mill the heads and run a thin gasket then dont i run into problems with the rockers? and with the intake lining up right?
 
The intake will fit fine. When you mill the heads they will mill the intake side of the heads also. You will likely need shorter push rods.
 
AdamR said:
The intake will fit fine. When you mill the heads they will mill the intake side of the heads also. You will likely need shorter push rods.
Click to expand...

Well i all ready have to get specila pushrods for the magnum heads. How do you know what length pushrods you need if you mill the heads?

also how much will it raise my compression if i mill it? I dont want to take to much off the heads.
 
AdamR said:
after 71 they dropped compression by moving the piston pin up. this dropped the piston way down in the bore about .100"

The earlier 318s that are rated in the 9:1 are are lower then that. probably in the *.5-8.8:1 range.

The real bad news is your 318 is likely in the 7.8:1 range.

The only way to know for sure what your compression is ,is to measure everything. Head CC's, Deck hieght and gasket thickness.
Click to expand...

Beside compressed thickness of the gasket you need to include the bore size of the gasket. Fel-Pro for instance is 4.150. That adds significant volume that will reduce the compression ratio even more.

If you are using pistons with valve reliefs that needs to be taken into account to.

Also, the advertised compression ratio for a piston typically is assuming some set of dimensions for all the other parts. You won't have that compression unless the parts are at the nominal numbers the piston manufacuturer used. In most all cases you will have a significantly lower compression ratio than wht the psiton is advertised for if the heads & block have not been decked.

Here is a nice little on line compression ratio calculator;
http://www.csgnetwork.com/compcalc.html
 
All im trying to figuer out is how much will the compression will go up if i but magnum heads on my stock 74 318.
 
my 318 is a 75 model, and i THINK its supposed to have like an 8.4:1 ration, but wouldnt be the least surprised if it were lower. i have stock smog heads with the egr passage and all that crap. i was going to have them rebuilt, but now im thinking i should toss them and get non-smog heads and a no-egr intake manifold. the head volume on mine is supposed to be 60cc too.
 
Sublime69 said:
All im trying to figuer out is how much will the compression will go up if i but magnum heads on my stock 74 318.
Click to expand...

Sounds like from what others have posted about stock 318 LA heads they have approximately the same size chambers. So in that case you can't expect to see any increase in the compression ratio.

However, the magnum heads have bigger valves and a better port design and will flow a lot better so you should see an increase in power.
 
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